The present disclosure generally relates to fluid control valves and systems. Fluid control valves may be used in systems for the controlled feeding of volatile fuel components present in the free space of a fuel tank into an intake manifold of an internal combustion engine. A system of this type is disclosed U.S. Pat. No. 4,901,702. The system includes a vent line connecting the free space to the atmosphere. In the vent line there is disposed a storage chamber containing an absorption element, as well as a line connecting the storage chamber to the intake tube, which can be shut off by an electromagnetic check valve. Between the check valve and the intake tube there is disposed an auxiliary valve with a control chamber. The auxiliary valve can be closed by a vacuum actuator in dependence upon the pressure difference between the control chamber and the atmosphere. During low engine operating speeds in the near idling range, the flow rate of volatile fuel components through the apparatus is reduced so as to prevent the excessive enrichment of the mixture fed to the engine; at high engine operating speeds when the differential pressure between the engine and the tank is reduced, the non-return valve employed is wide open.
Another system of this type is disclosed in U.S. Pat. No. 5,284,121. This system comprises a pneumatically actuated purge control valve for opening or closing a flow line which connects an upper space of the fuel tank with the intake pipe, a controller for controlling the operation of the valve, a throttle section formed in series with the purge control valve, and pressure and temperature sensors which are located on the upstream side of the throttle section for detecting a pressure and a temperature of the evaporated fuel. When a value detected by the pressure sensor exceeds a predetermined value of pressure for providing a critical pressure ratio at which a flow rate of the evaporated fuel at the throttle section substantially equals to a sonic velocity, the controller opens the pneumatically actuated purge control valve to cause a purged flow of the evaporated fuel whose flow rate is constant. Simultaneously, the controller calculates a purged flow rate of the evaporated fuel from the detected values of the pressure and temperature sensors and a time period during which the purge control valve is opened. On the basis of the calculated purged flow rate, a reduction correction is made to an amount of the fuel to be supplied to the engine in order to maintain an air-fuel ratio in the optimum condition.
U.S. Pat. No. 5,460,137 provides another system of this type. This system includes a venting line that connects the free space of the fuel tank to the atmosphere. Along this line is interposed a storage chamber containing an absorption element having at least one line which connects the storage chamber to the intake manifold and which can be sealed by an electromagnetically actuated valve. The valve includes a seat and a Laval-type nozzle arranged downstream of the seat. The Laval-type nozzle allows the valve to employ a valve seat having a relatively small orifice cross section while maintaining generally the same mass throughput as a valve employing a relatively large valve seat with a standard cylindrical nozzle. The relatively small orifice cross section allows the valve to employ relatively small actuating forces to open and close the valve, thereby allowing the valve to be held in the closed position during clocked control for a longer period of time so that the excessive enrichment of the fuel-air mixture can be avoided.
Disclosed herein is a fluid control valve comprising a valve seat and a nozzle proximate the valve seat. The nozzle includes a convergent section and a divergent section formed by a semi-circular profile.
Also disclosed herein is a system for controlled feeding of volatile fuel components from a free space of a fuel tank to an engine manifold. The system comprises a storage chamber in fluid communication with the free space of the fuel tank, and a valve in fluid communication between the storage chamber and the engine manifold. The valve includes a valve seat and a nozzle proximate the valve seat. The nozzle includes a convergent section and a divergent section formed by a semi-circular profile.